我如何处理一个购物篮，其中有很多产品的成本计算可能不同

我正在做一项任务，我至少有几个产品有问题，例如买一送一，买 4 送一，买 5 并获得 20% 的折扣。现在我想知道我应该怎么做来处理这样的问题，因为当我遇到更多的产品时，产品计算的代码库会失控。这里最好的解决方案是什么？目前我所做的是根据每个产品代码创建一个类，并且产品的计算在该文件中是本地的。对象构造是通过静态工厂方法完成的。关于算法改进的任何建议，如果我可以进一步减少代码并使其简单，那就太好了。

class BOGOFCalculator implements BasketPriceCalculator
{
    const MIN_ITEMS_REQUIRED_FOR_DISCOUNT = 2;

    /**
     * @param Product $product
     * @param integer $totalItems
     * @return float
     */
    public function calculate(Product $product, $totalItems): float
    {
        return $this->calculateFullPrice($product, $totalItems) - $this->calculateDiscount($product, $totalItems);
    }

    /**
     * @param Product $product
     * @param $totalItems
     * @return float
     */
    private function calculateFullPrice(Product $product, $totalItems): float
    {
        return $product->getPrice() * $totalItems;
    }

    /**
     * @param Product $product
     * @param $totalItems
     * @return float
     */
    private function calculateDiscount(Product $product, $totalItems): float
    {
        return $product->getPrice() * floor($totalItems/static::MIN_ITEMS_REQUIRED_FOR_DISCOUNT);
    }
}

篮子看起来像下面

class Basket
{
    /**
     * @param Product[] $products
     *
     * @return float
     */
    public function calculateProductTotal(Product ...$products): float
    {
        $totalItemsOfEachProduct = $this->getTotalItemsOfEachProductInTheBasket(...$products);
        $items = $this->getDistinctProductsInTheBasketWithQuantity(...$products);
        $total = 0;
        foreach ($items as $productCode => $item) {
            /** @var BasketPriceCalculator $priceCalculator */
            $priceCalculator = PriceCalculatorFactory::getInstance($productCode);
            $total += $priceCalculator->calculate($item, $totalItemsOfEachProduct[$productCode]);
        }

        return $total;
    }

    /**
     * @param Product[] $products
     *
     * @return array
     */
    private function getTotalItemsOfEachProductInTheBasket(Product ...$products): array
    {
        $totalItemsPerProductCode = array_map(function ($product) { return $product->getCode(); }, $products);

        return array_count_values($totalItemsPerProductCode);
    }

    /**
     * @param Product[] $products
     *
     * @return array
     */
    private function getDistinctProductsInTheBasketWithQuantity(Product ...$products): array
    {
        $items = [];
        foreach ($products as $product) {

            if (!array_key_exists($product->getCode(), $items)) {
                $items[$product->getCode()] = $product;
            }
        }

        return $items;
    }
}